Recently, due to the global growth of population and the broad industrial developments including emerging countries, the fresh-water-generation demands of the drinking water and the industrial water in the desert areas or the like have become definite.
Formerly, there has been a desalination system S100 shown in FIG. 5, as a system for desalinating the sea-water and the sewage water.
The production of the product water s101 (the industrial water) utilizing the sewage water in the desalination system S100 is executed as following. Incidentally, the salinity concentration of the sewage water is approximately 0.1%.
The sewage water is water-supplied to the MBR (Membrane Bioreactor) 101 by the pump p101, and the activated sludge or the like of the solid contents in the sewage water is removed by the MBR 101, then the MBR permeable water which has permeated the MBR 101 is water-supplied to the low-pressure RO membrane (Reverse Osmosis Membrane) 102 by the pump p102.
Incidentally, the MBR permeable water which has permeated the MBR 101 has the salinity concentration of approximately 0.1% which is low, therefore, as the RO membrane, the low-pressure RO membrane 102 which is an RO membrane (reverse osmosis membrane) of the low-pressure of approximately 1 to 2 MPa (mega-pascal) is utilized.
By permeating the low-pressure RO membrane 102, almost a half of the concentrated-water s104 including the impurities of the salinity or the like is removed, and the MBR permeable water water-supplied by the pump p102 is desalinated, then the industrial water of the remaining half of product water s101 is produced.
To the contrary, the concentrated-water s104 which includes the impurities of the salinity or the like removed by the low-pressure RO membrane 102 and is approximately ½ in volume of the sewage water concentrated to the salinity concentration of approximately 0.2%, is water-supplied from the low-pressure RO membrane 102 to the stirring-vessel 104.
The production of the industrial water which is the product water s102 from the sea-water in the desalination system S100 is executed as following. Incidentally, the salinity concentration of the sea-water is 3 to 4% approximately.
The sea-water is water-supplied to the UF membrane 103 by the pump p103, and water-supplied to the stirring-vessel 104, removing particles by the UF membrane 103. In the stirring-vessel 104, the UF membrane permeation sea-water which has permeated this UF membrane 103 and the concentrated-water s104 which is approximately ½ in volume of the sewage water concentrated from the sewage water by the aforementioned low-pressure RO membrane 102 are stirred and water-supplied to the intermediate-pressure RO membrane 105 by the pump p104, thereafter.
The UF membrane permeation sea-water which has permeated the UF membrane 103 has the salinity concentration of 3 to 4%, however, it is diluted by the concentrated-water s104 of the salinity concentration of 0.2%, accordingly, the intermediate-pressure RO membrane 105 of the RO membrane (reverse osmosis membrane) of approximately 3 to 5 MPa of the intermediate-pressure is utilized.
Of the mixture water s103 which has been water-supplied from the stirring-vessel 104 to the intermediate-pressure RO membrane 105 by the pump p104, by permeating the intermediate-pressure RO membrane 105, approximately ½ is removed as the brine water s105 including the impurities of the salinity or the like, and the remaining approximately ½ is produced as the desalinated product water s102 (the industrial water). In other words, the industrial water of the product water s102 is produced as ½ of the sea-water plus approximately ¼ of the sewage water in volume.
To the contrary, the brine water s105 which has been concentrated in the approximately twice the salinity concentration of the mixture water s103 including the impurities of the salinity or the like removed by the intermediate-pressure RO membrane 105, is removed from the intermediate-pressure RO membrane 105. In other words, the brine water s105 is drained as ½ of the sea-water plus approximately ¼ of the sewage water in volume.
Incidentally, the pressure energy of the brine water s105 is recovered as the rotational energy by the energy recovery device 106, and is utilized as the power source (energy source) of the pressure-transfer to the intermediate-pressure RO membrane 10 of a part of the mixture water s103 which has by-passed the pump p104.
As another conventional desalination system, there is a desalination system S200 shown in FIG. 6.
The desalination system S200 doesn't supply the concentrated-water s104 of the sewage water in the desalination system S100 of FIG. 5 to the stirring-vessel 204, and constitutes the desalination of the sewage water and the desalination of the sea-water independently.
In the desalination system S200, the sea-water with the high the salinity concentration is not diluted by the supply from the sewage water (the concentrated-water s104 of the sewage water of FIG. 5) by the stirring-vessel 204, therefore, the high-pressure RO membrane 205 which has the salinity concentration as high as approximately 3 to 4% and the high-pressure of approximately 6 to 8 MPa is utilized.
The other configuration is similar to the desalination system S100 of FIG. 5, accordingly, the components of the desalination system S100 are shown with references in the two-hundred range and the in-depth descriptions are omitted.
In the desalination system S200, the sewage water permeates the low-pressure RO membrane 202 and is desalinated, and the industrial water which is the product water s201 of approximately a half of the sewage water can be acquired. To the contrary, the sea-water permeates the high-pressure RO membrane 205 and is desalinated, and the drinking water which is the product water s202 of a ½ amount of the sea-water can be acquired.
The conventional desalination system S100 (See FIG. 5) has following advantages, compared to the desalination system S200 (See FIG. 6).
Firstly, in the desalination system S100 of FIGS, the drainage (the concentrated-water s104) removed in the process for fresh-water-generating the product water s101 from the sewage water is utilized in the process for fresh-water-generating the product water s102 from the sea-water, therefore, there are advantages to be capable of increasing the production amount of the product water from the sea-water.
More specifically, in the case not to utilize the drainage (the concentrated-water s104) from the sewage water, regarding the product water from the sea-water, it is possible to water-intake more industrial water of the product water s102 as much as the water-increased volume of approximately ½ of the sewage water, in place of the approximately ½ of the sea-water in volume.
Secondly, regarding the sea-water (the salinity concentration 3 to 4% approximately), the concentrated-water s104 (the salinity concentration 0.2% approximately) in the low-pressure RO membrane 102 of the sewage water is added, therefore, the sea-water is diluted and the salinity concentration is decreased. Therefore, in the case not to utilize the drainage (the concentrated-water s104) from the sewage water, the high-pressure RO membrane was required because the sea-water has the high the salinity concentration, however, due to the dilution by the concentrated-water s104, the intermediate-pressure RO membrane 105 is sufficient, and the power of the pump p104 can be decreased, compared to the case of the high-pressure RO membrane.
Incidentally, in comparison with the permeation pressure of the intermediate-pressure RO membrane of approximately 3 to 5 MPa, the permeation pressure of the high-pressure RO membrane is approximately 6 to 8 MPa, and in order to permeate the high-pressure RO membrane, the larger power (energy) than the intermediate-pressure RO membrane is required.
Incidentally, there is Patent Literature 1 as a prior art reference in respect of the present invention.